The present invention concerns a bottom construction for a boat, as specified in the preamble to claim 1.
In designing the bottom structure of fast, planing boats endeavours are to minimize the water resistance, or the wet surface area of the boat, at the same time maintaining good running characteristics, directional stability and steerability of the boat.
One has in prior art attempted to improve the running characteristics of a boat by means of various transversal step designs with which the water flows are guided in desired manner underneath the bottom, and by which the boat is made to rise higher, thereby reducing the wet surface. Likewise known in bottom designs of prior art are various grooves, channels and other guides longitudinal to the boat, by which one attempts to maximize the favourable action of water flows under the bottom.
The problem associated with most bottom designs of prior art is, however, their high planing ascent threshold, that is, when the speed is accelerated the bow of the boat rises up steeply, and only after having gained a certain speed the bow sinks down and the boat rises and begins to plane. However, the boat keeps planing even at considerably lower speed.
The second problem with boats of prior art consists of its planing properties in sharp curves. If the hull shape in boats of prior art at all enables sharp turns at high speed, the hull sinks to rather great depth in the water, as a consequence of which the speed of the boat drops strongly, whereafter the planing ascent threshold has to be exceeded once more, in order to regain the original speed.
The third problem in fast boats of prior art consists of the powerful centrifugal forces in curves, a circumstance which significantly impedes any work done in a fast-moving boat. It also causes operating trouble in the case of various pieces of technical equipment, e.g. the armament which naval forces use in fast boats.